Does an admission of lineage by two just men who are co-heirs establish that lineage if another heir exists?

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The admission of lineage by two just men who are co-heirs does not establish the lineage if another heir besides them exists, unless they provide testimony (shahada) to that effect. This view is held by Al-Shafi'i. The basis for this ruling is that it constitutes an admission made by only a portion of the heirs, and thus, it cannot establish lineage, similar to the case of a single person admitting lineage. This differs from formal testimony because testimony requires justice ('adala) and masculinity, whereas an admission does not carry the same requirements.